5Earth Science and Applications from Space

Unlike the other roadmap committees, the committee that produced Exploring Our Planet for the Benefit of Society: NASA Earth Science and Applications from Space Strategic Roadmap1 had no NRC decadal survey to guide it. Past NRC studies have articulated the importance of broad community discussion and input as an essential part of NASA’s long-term strategic planning.2,3 Although the Earth science roadmap committee included representatives from NASA, the National Oceanic and Atmospheric Administration, industry, and academia, much broader community input will be available after completion of the NRC decadal survey in Earth science that is currently in progress and scheduled for completion in 2006. The panel recommends that the forthcoming NRC Earth science and applications decadal survey be used as a starting point for mid- to long-term planning (i.e., for beyond 2010). Prior to the completion of the decadal survey, NASA planning and advanced technology programs should remain flexible to avoid commitments to missions that might not receive broad community support. In the near term NASA should focus on the roadmap recommendation that NASA “complete the approved [Earth sciences] program in a timely fashion, including the next Earth System Science Pathfinder Announcement of Opportunity,” and on the specific recommendations made in the NRC decadal survey interim report issued in April 2005.4

REVIEW OF PROPOSED OBJECTIVES

The Earth science roadmap committee appropriately focused more on Earth science in its own right rather than on studying Earth as a benchmark or testbed for research to be carried out under the vision for space exploration. The roadmap is built around six guiding science questions, all of which have some heritage in previous science strategy documents (e.g., NASA’s Earth Science Research Plan and plans for the U.S. Climate Change Science Program). The roadmap rightly focuses on the specific measurements that are required to meet the science objectives, rather than on missions.

The roadmap advocates five separate “lines of inquiry,” corresponding to five of the six guiding science questions in the roadmap. These five lines of inquiry largely follow traditional scientific disciplines: atmospheric composition, climate and weather, water, life, and solid Earth. The panel believes that by pursuing a strictly disciplinary approach for the lines of inquiry, NASA may impede advances in areas that are considered to be cross-disciplinary. The sixth science question (What role do human systems play in driving changes in the Earth system?) is treated as a crosscutting issue, and no line of inquiry is proposed for this question.

The selection and sequencing of the scientific objectives are neither thoroughly nor convincingly explained in the roadmap, and there are some serious gaps. Notably, the roadmap omits program elements that are critical to current NASA responsibilities in the Climate Change Science Program, largely in ocean and terrestrial science. As an example, the roadmap’s life program encompasses a number of science areas and gives emphasis to biogeochemical cycles. It is responsive to the vision for space exploration, but it omits aspects of land use and land cover change, ecosystems, and biodiversity and their associated measurement needs. The reason for that omission is not explained.

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5
Earth Science and Applications from Space
Unlike the other roadmap committees, the committee that produced Exploring Our Planet for the Benefit of Society: NASA Earth Science and Applications from Space Strategic Roadmap1 had no NRC decadal survey to guide it. Past NRC studies have articulated the importance of broad community discussion and input as an essential part of NASA’s long-term strategic planning.2,3 Although the Earth science roadmap committee included representatives from NASA, the National Oceanic and Atmospheric Administration, industry, and academia, much broader community input will be available after completion of the NRC decadal survey in Earth science that is currently in progress and scheduled for completion in 2006. The panel recommends that the forthcoming NRC Earth science and applications decadal survey be used as a starting point for mid- to long-term planning (i.e., for beyond 2010). Prior to the completion of the decadal survey, NASA planning and advanced technology programs should remain flexible to avoid commitments to missions that might not receive broad community support. In the near term NASA should focus on the roadmap recommendation that NASA “complete the approved [Earth sciences] program in a timely fashion, including the next Earth System Science Pathfinder Announcement of Opportunity,” and on the specific recommendations made in the NRC decadal survey interim report issued in April 2005.4
REVIEW OF PROPOSED OBJECTIVES
The Earth science roadmap committee appropriately focused more on Earth science in its own right rather than on studying Earth as a benchmark or testbed for research to be carried out under the vision for space exploration. The roadmap is built around six guiding science questions, all of which have some heritage in previous science strategy documents (e.g., NASA’s Earth Science Research Plan and plans for the U.S. Climate Change Science Program). The roadmap rightly focuses on the specific measurements that are required to meet the science objectives, rather than on missions.
The roadmap advocates five separate “lines of inquiry,” corresponding to five of the six guiding science questions in the roadmap. These five lines of inquiry largely follow traditional scientific disciplines: atmospheric composition, climate and weather, water, life, and solid Earth. The panel believes that by pursuing a strictly disciplinary approach for the lines of inquiry, NASA may impede advances in areas that are considered to be cross-disciplinary. The sixth science question (What role do human systems play in driving changes in the Earth system?) is treated as a crosscutting issue, and no line of inquiry is proposed for this question.
The selection and sequencing of the scientific objectives are neither thoroughly nor convincingly explained in the roadmap, and there are some serious gaps. Notably, the roadmap omits program elements that are critical to current NASA responsibilities in the Climate Change Science Program, largely in ocean and terrestrial science. As an example, the roadmap’s life program encompasses a number of science areas and gives emphasis to biogeochemical cycles. It is responsive to the vision for space exploration, but it omits aspects of land use and land cover change, ecosystems, and biodiversity and their associated measurement needs. The reason for that omission is not explained.

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The roadmap defines integration objectives that progress from “exploration and discovery” to “continuous awareness” and “developing perspectives.” These are artificial constructs that create confusion. The roadmap also defines a Measurement Maturity Index for space-based measurements, which “encapsulates both the scientific maturity of a measurement and its readiness to transition to operational use.”a Although the Measurement Maturity Index framework is potentially valuable, it will need considerably more development to be useful in setting priorities for missions. The roadmap discussion of the index does not specify whether all measurement sets are expected to progress linearly and completely through each of the index’s stages, or whether there may be measurement sets for which only some of the stages are relevant. In addition, the readiness of a measurement needs to be weighted by the scientific (and societal) importance of the measurement.
Although the roadmap is titled Exploring Our Planet for the Benefit of Society, the applications component of the roadmap is inadequately developed. The NRC decadal survey interim report states that “a central responsibility for the coming decade is to ensure that established societal needs help guide scientific priorities more effectively and that emerging scientific knowledge is actively applied to obtain societal benefits.”5 There are several pressing societal issues, such as global food and water security, biodiversity loss, and pollution in coastal zones, that will be exacerbated over the coming decades and that can be informed by NASA science and observations. The applications “lines of inquiry” of the roadmap have yet to be developed, and they need to be closely coupled to both the science and the planned measurements, driven by societal needs, and developed in close communication with the stakeholders. The panel recommends that as part of long-term planning, NASA develop the applications aspects of its Earth sciences program to a greater degree than was done in the roadmap and strengthen the linkage between the science and applications program components.
REVIEW OF PROPOSED IMPLEMENTING PROGRAMS
The NASA Earth science roadmap committee assumed that the missions currently in formulation would be implemented, “providing a foundation for the roadmap.” As noted by the NRC decadal survey interim report, the delay in some of these missions “jeopardizes NASA’s ability to fulfill its obligations” in areas such as climate change research, and the reduced number of Earth System Science Pathfinder (ESSP) missions limits important innovative contributions from the smaller principal investigator-led instruments.6
The roadmap’s mission timeline advocates a sequential phasing of the five lines of inquiry from exploration to perspective, beginning with atmospheric composition, climate/weather, and water, followed by life and solid Earth. This approach, adopted apparently because of budget concerns and previous investments, is a serious weakness. NASA needs to maintain its scientific inquiry and capabilities in multiple focus areas concurrently. This will allow for continued discovery and will support the integrated view of Earth system science that is unique to the agency.
A closer connection is needed between the science rationale and priority for the proposed missions. For example, the contribution of the Biosignatures mission to Earth science is not articulated.
The goal of the phase-3 implementation stage in the roadmap is to have a fully instrumented observing system in the third decade. However, some components of the observing system are needed now to provide critical ongoing contributions to science (e.g., as recommended by the Intergovernmental Panel on Climate Change) and applications (e.g., via the Global Earth Observation System of Systems). The Earth observing system needs to be designed now and built incrementally, and it needs to be adaptable to incorporate technological improvement.
In order to plan for the types of long-term measurements that are required for climate studies, the roadmap anticipates transitioning measurement techniques from research to operations. If this transition
a
The Measurement Maturity Index is a counterpart to NASA’s longstanding “Technology Readiness Level” index, which represents maturity of a technology for end use.

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is to be viable, NASA will need to start by addressing both the current institutional and financial obstacles to transition.7,8 Similarly, the approach to decision support requires a closer interaction with the stakeholder community.
The roadmap includes plans through 2035. Although such a long planning timeline is needed for other components of the vision for space exploration, such as Mars exploration, there is little point in trying to anticipate the Earth science observation priorities so far in advance. The roadmap foresees some transformational new technologies for the later years of its three-decade planning period, including for example, a blue/green lidar to profile the upper ocean. Such technologies potentially will provide new insights into the Earth system, although at present it would seem premature to predict what breakthroughs might develop in the coming decades. While the roadmap explores a variety of new technologies, broad community input will help in identifying transformational technologies that should be developed for Earth science missions. For example, small satellites could provide important flexibility to the overall program, and the land observation community could consider a constellation of small-satellite imagers to augment the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Operational Land Imager mission.9 The NRC Earth science decadal survey interim report recommends some additional areas in which enabling technology is needed.10
GAPS, OPPORTUNITIES, AND INFRASTRUCTURE
Although the roadmap attempts to capture the breadth of Earth science, there are important measurements that appear to have been neglected, for example, water vapor, air-sea heat fluxes, and land-cover change.
As would be expected, the Earth science roadmap appears to have minimal overlap with the other roadmaps, aside from a shared interest with the Sun-Solar System Connection roadmap in examining the relationships between solar variability and climate change, possibly with a flagship mission at the Lagrangian point 1 (L1). The Sun-solar system roadmap, however, appears to assign the L1 mission a secondary priority. The panel cautions that the L1 mission should not be given high overall priority merely because it appears in both the Sun-solar system and Earth science roadmaps. Rather, the relevance of the L1 mission should be thoroughly evaluated for Earth sciences before determining its overall priority. In integrating the roadmaps, NASA will need to balance shared objectives among roadmaps and the resources required to achieve them. The panel understands that the Earth science roadmap committee had little time to explore possible opportunities to share science or technology between roadmaps. The roadmap integration process should identify and evaluate such opportunities.
A number of issues that cut across the many subdisciplines represented in the Earth science roadmap need special attention, particularly with regard to non-satellite infrastructure. For example, the role of data systems and management is addressed only in passing. Given that data management has proved to be a major challenge for NASA in the past, next-generation data management systems need careful consideration within the roadmap and need to be an integral part of mission planning.
The roadmap draws attention to information and computing technology needs and advocates development of systems that merge observations into models through “data assimilation” to provide best estimates of the Earth system. Modern-day weather forecast models depend on data assimilation, and data assimilation systems are now being developed for other aspects of Earth science. Nonetheless, satellite data are important in their own right and not just as inputs to assimilating models. Both model and product validation are crosscutting issues, and product validation needs to be an integral part of the budget planning for each mission.

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SCHEDULE, RESOURCES, AND PARTNERSHIPS
The timing of certain missions in the roadmap appears to be delayed relative to the information needs. For example, the Carbon Cycle Strategic Plan in the Climate Change Science Program states that “continued satellite land-cover data products and new remote sensing estimates of above ground biomass will be needed” to carry out carbon monitoring.11 Given the investment already made in the Vegetation Canopy Lidar, the proposed 2015 launch date for a vegetation structure instrument may need reconsideration. Similarly the proposed mission sequence will result in some immediate and serious gaps in data continuity. For example, the Landsat 7 scan line corrector developed a malfunction in 2003, but its successor, the Operational Land Imager (OLI), is not scheduled for launch until 2010. Without a bridging mission, there will be a serious break in land data continuity.12
The near-term technological development appears to be realistic, but there is insufficient detail in the roadmap to permit an in-depth evaluation. For example, the rationale and technological approach for the Cal/Val mission need further elaboration. The out-year missions are not well enough developed to evaluate their technological feasibility.
The Earth science roadmap assigns missions to single lines of inquiry, even if mission measurements are relevant to more than one line of inquiry. For example, the Orbiting Carbon Observatory is listed as an atmospheric composition mission but could also be considered a climate mission and a life mission. This narrow focus could exclude ancillary science if requirements for broader science questions were not considered early in the design phase.
Unlike with the other roadmaps, the near-term missions and the budget implications or trade-offs between the different missions were not discussed in the Earth science roadmap. The science community needs to be aware of the potential costs of different missions and to be involved in the discussion of trade-offs between larger and smaller missions and the associated science implications.
The roadmap is essentially a NASA-alone plan, aside from the stated intent to transfer mature observational methods to operations. Interagency cooperation is critical for ensuring long-term operational measurements, and an ongoing dialogue concerning mission planning will be needed with NOAA, which plays a strong role in atmospheric and ocean observations.13 NASA could utilize the Climate Change Science Program Observation Working Group for mission planning in an interagency context. International cooperation also will be important in implementing and enhancing the NASA program. The roadmap does not explore the opportunities that are afforded to NASA by international cooperation in Earth observation via the Committee on Earth Observation Satellites and the emerging Global Earth Observation System of Systems (GEOSS) and the final plan from the Interagency Working Group on Earth Observation.14,15
SCIENTIFIC RESEARCH SUPPORT FOR THE VISION FOR SPACE EXPLORATION
The NRC panel was also tasked with evaluating how the Earth science roadmap provides scientific research support for the vision for space exploration. The panel recognizes that the Earth science roadmap is distinctly different from the space science roadmaps. Earth and space science have different histories in NASA. The Earth science roadmap is not strongly coupled to the exploration objectives, but it does directly respond to the NASA goals “to improve life here” and “to know our origin and destiny.”b Earth science at NASA also has a number of external pressures on its near- and mid-term planning, including the requirement to contribute to a number of national imperatives such as the Climate Change Science Program, the Interagency Working Group on Earth Observation, the Commercial Remote Sensing and the Land Remote Sensing Space Policies, and international commitments such as the Intergovernmental Panel on Climate Change and GEOSS. The breadth of NASA’s multidisciplinary
b
M. Allen and P. Hertz, “NASA Roadmaps and Science Integration,” presentation to Review of NASA Strategic Roadmaps: Science Panel, Washington, D.C., June 13, 2005.

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Earth science program is greater than that of the programs covered by the other roadmaps, and there is the additional challenge of addressing both science and applications.
Recognizing the strong message from the NRC decadal survey interim report that “NASA must retain Earth science as a central priority, to support critical improvements in understanding the planet and developing useful applications,”16 the panel recommends that NASA strongly support the Earth science program independent of its involvement in the vision for space exploration.
REFERENCES
1. National Aeronautics and Space Administration (NASA), Advanced Planning and Integration Office. 2005. Exploring Our Planet for the Benefit of Society: NASA Earth Science and Applications from Space Strategic Roadmap. NASA, Washington, D.C. Available at <www.hq.nasa.gov/office/apio/pdf/earth/earth_roadmap.pdf>.
2. National Research Council (NRC). 1999. “Assessment of NASA’s Plans for Post-2002 Earth Observing Missions,” letter from SSB chair Claude R. Canizares, Task Group chair Marvin A. Geller, Board on Atmospheric Sciences and Climate co-chairs Eric J. Barron and James R. Mahoney, and Board on Sustainable Development chair Edward A. Frieman to Dr. Ghassem Asrar, NASA’s associate administrator for Earth Science, April 8. The National Academies Press, Washington, D.C. Available at <www.nap.edu/books/NI000342/59.html>.
3. NRC. 2003. “Assessment of NASA’s Draft 2003 Earth Science Enterprise Strategy: Letter Report,” letter from SSB chair John H. McElroy to Dr. Edward J. Weiler, NASA’s associate administrator for the Office of Space Science, May 29. The National Academies Press, Washington, D.C. Available at <www.nap.edu/books/NI000421.html>.
4. NRC. 2005. Earth Science and Applications from Space: Urgent Needs and Opportunities to Serve the Nation [interim report]. The National Academies Press, Washington, D.C.
5. NRC. 2005. Earth Science and Applications from Space [interim report], p. 10.
6. NRC. 2005. Earth Science and Applications from Space [interim report], p. 2.
7. NRC. 2000. From Research to Operations in Weather Satellites and Numerical Weather Prediction: Crossing the Valley of Death. National Academy Press, Washington, D.C.
8. NRC. 2001. Transforming Remote Sensing Data into Information and Applications. National Academy Press, Washington, D.C.
9. NRC. 2000. The Role of Small Satellites in NASA and NOAA Earth Observation Programs. National Academy Press, Washington, D.C.
10. NRC. 2005. Earth Science and Applications from Space [interim report].
11. Climate Change Science Program. 2003. Strategic Plan for U.S. Climate Change Science Program. July. Available at <www.climatescience.gov/Library/stratplan2003/final/ccspstratplan2003-all.pdf>, p. 77.
12. NRC. 2005. Earth Science and Applications from Space [interim report].
13. NRC. 2005. Ensuring the Climate Data Record from the NPP and NPOESS Meteorological Satellites. The National Academies Press, Washington, D.C.
14. Group on Earth Observations. 2005. GEOSS 10-Year Implementation Plan. February. ESA Publications Division. Available at <earthobservation.org/docs/GEOSS%2010Year%20Implementation%20Plan%20(GEO%201000).pdf>.
15. National Science and Technology Council. 2005. Strategic Plan for the U.S. Integrated Earth Observation System. April 6. Available at <iwgeo.ssc.nasa.gov/docs/EOCStrategic_Plan.pdf>.
16. NRC. 2005. Earth Science and Applications from Space [interim report], p. 14.